1. Technical Field of the Invention
The present invention relates to the formulation of travoprost compositions useful to induce or stimulate the growth of hair shafts and in particular, human hair and eyelashes.
2. Description of Background and/or Related and/or Prior Art
In human beings, the growth of the hair is cyclical and comprises three successive phases: the anagen phase, the catagen phase and the telogen phase. Each follicle of the hair is thus continually replaced, cyclically and independently of the adjacent follicles. The anagen phase or growth phase, during which the hair lengthens, lasts several years. The catagen phase, which succeeds the anagen phase, is very short and lasts only a few weeks. During this phase, the hair undergoes an involution, the follicle atrophies and its implantation in the skin appears less and less deep. The telogen phase, which lasts several months, corresponds to a period of rest of the follicle, where the hair finishes by falling out. After this resting phase, a new follicle is regenerated there and a new cycle recommences.
At any moment, not all the hairs are in the same phase at the same time. Thus, out of the approximately 150,000 individual hairs which make up the hair, only approximately 10% of them are at rest and will thus be replaced in a few months according to a biological clock specific to each hair.
In the mouse and other furry mammals, the hair follicles also have a replacement cycle comprising the three anagen, catagen and telogen phases; however, the hair cycles are often “synchronized”, that is to say in the same phase of the cycle at the same time in the same region.
The natural loss of the hair can be estimated, on average, at a few hundred hairs per day for a normal physiological state. However, it happens that the hair cycle can go wrong and that hair loss accelerates and results in a temporary or definitive loss of the hair known as alopecia. An alopecia can be caused in different ways.
It may involve a massive loss of or detrimental changes in the hair known as telogen effluvium, after pregnancy, during conditions of undernourishment or dietary imbalances, or also during conditions of asthenia or hormonal dysfunctioning, as may be the case during or after the menopause. It may also involve loss of or detrimental changes in the hair in connection with seasonal phenomena. In certain dermatosis conditions of the scalp with an inflammatory nature, such as, for example, psoriasis or seborrheic dermatitis, hair loss can be greatly increased or can result in highly disrupted cycles of the follicles.
It may also be a matter of alopecia, which is essentially due to a disturbance of hair replacement which results, first, in an acceleration in the frequency of the cycles at the expense of the quality of the hair and then of its amount. The successive growth cycles result in hair which is increasingly fine and increasingly short and which is gradually converted to an unpigmented down. Areas are preferentially affected, in particular the temples or the front of the head, in men, and, in women, a diffuse alopecia of the vertex is observed.
It is a matter more particularly of androgenic alopecia. In a significant number of cases, early hair loss takes place in genetically predisposed subjects; it is then a matter of androchronogenetic alopecia. This form of alopecia affects men in particular.
Furthermore, it is known that certain factors, such as hormonal imbalance, physiological stress or malnutrition, can accentuate the phenomenon.
The term alopecia also covers an entire family of conditions of the hair follicle having as a final consequence partial or general definitive hair loss.
For many years, in the cosmetic or pharmacy industry, compositions have been solvent which make it possible to eliminate or reduce alopecia and in particular to induce or stimulate hair growth or to decrease hair loss.
From this viewpoint, a large number of compositions comprising very diverse active principles, are known, such as, for example, 2,4-diamino-6-piperidinopyrimidine 3-oxide or “minoxidil”, described in U.S. Pat. Nos. 4,139,619 and 4,596,812, or its numerous derivatives, such as those described, for example, in EP-0353123, EP-0356271, EP-0408442, EP-0522964, EP-0420707, EP-0459890 and EP-0519819.
Clinical studies have demonstrated that PGF2α analogues have the property of bringing about the growth of body hairs and eyelashes in man and animals (Murray A and Johnstone M D, 1997, Am. J. Opht., 124(4), 544-547). In man, tests carried out on the scalp have shown that a prostaglandin E2 analogue (viprostol) has the property of increasing hair density (Roenigk H H., 1988, Clinic. Dermatol. 6(4), 119-121).
WO 98/33497 describes pharmaceutical compositions comprising prostaglandins or prostaglandin derivatives useful to combat hair loss in man. Prostaglandins of the A2, F2α and E2 type are preferred.
Travoprost, alone or in combination, has been provided for stimulating hair growth when applied daily (WO 03/009820, EP-1352629 and EP-1358868).
However, from the above it will be seen that the majority of the products intended to combat hair loss and/or to induce hair regrowth exhibit a demanding dosage for the patient as the administration has to be carried out daily or twice daily. In particular, the dosage recommended for minoxidil, at the dose of 2%, is a twice-daily administration.
Thus, a product with an effectiveness comparable to or greater than that of the products already existing, but which is administered less frequently, i.e., from non-daily to weekly, indeed even twice monthly, will present a major advantage for the patient in terms of comfort and safety of use.
There thus exists a real need to identify and/or develop a product with a less restrictive dosage which would not require daily or twice-daily administration to be as effective, indeed even more effective, than those products identified above.